Rob Dyrdek Remembers Friend & Co-Star Christopher 'Big Black' Boykin: 'My Heart is Broken'

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Rob Dyrdek is reeling from the loss of his friend and former co-star, Christopher "Big Black" Boykin, who died Tuesday morning.

The 42-year-old skate boarder-turned-TV personality took to Twitter following the news of Boykin's death, and shared a series of heartfelt tweets paying tribute to his pal's life and their iconic friendship.

WATCH: ‘Rob & Big’ Star Christopher 'Big Black' Boykin Dies at 45

"My heart is broken," Dyrdek wrote in the caption of a photo of him and Boykin sitting together on a large swing. "I don't want write this post. I don't want to believe that this is reality. I am so thankful for you."

Boykin was Dyrdek's close friend and co-star on their hit MTV reality series, Rob & Big, from 2006 to 2008, and appeared on several of Dyrdek's later MTV shows, including Ridiculousness and Fantasy Factory.

"We truly were brothers that lived an unexpected unforgettable adventure. I just can't fathom that it would end so suddenly," Dyrdek tweeted. "You will forever be in my heart."

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The reality star also posted a sweet, funny snapshot of Boykin cradling Dyrdek's 10-month-old son, Kodah Dash, sharing, "I am so thankful for this moment... thank you for being an amazing human being and brother."

Boykin died Tuesday morning
, reportedly from a heart attack, at the age of 45. He is survived by his 9-year-old daughter, Isis.

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